1. Field of the Invention
The invention relates to an enhanced circuit board arrangement for a computer, such as a deskside personal computer, for example, and in particular, to an enhanced arrangement of a backplane, processor cards, memory cards, and clock card within a cage.
2. Background Information
Backplanes are wiring boards used in computers, and are typically provided with card slots or plugs for various circuit boards, such as a processor card and a so-called memory riser card, attached to a common surface of the backplane in the card slots or to the plugs. Further, it is typical to permanently attach a clock card, which is a further type of circuit board, to the common surface of the backplane. This assembly of the backplane and various circuit boards may be positioned within an open cage, which is a frame fixed within a computer housing. The cage serves to position the circuit boards within the computer housing.
It has generally been believed that each of the cards attached to the backplane needs to remain accessible for service or modification. As such, the number of cards that can be attached to the backplane has been limited by the front surface area of the backplane. As the processing and/or memory requirements of computers have increased, the required surface area of the backplane has likewise increased a corresponding amount to accommodate extra processor and/or memory riser cards, for example. However, the backplane is a relatively expensive computer component, and represents a significant portion of the total production cost of a computer system. As the size of the backplane is increased, the cost of the backplane disadvantageously increases a proportional amount, thereby increasing the production cost of an associated computer system. Therefore, a need exists for a way to satisfy the expanding needs for greater computer system processing power and/or memory capacity while keeping backplane costs under control.
Typical memory riser cards are provided with a plurality of removable Dual In-Line Memory Modules (DIMMs), which can be inserted into electrical slots provided on a surface of the cards. Further, the memory riser cards are typically provided in a commercial system with empty electrical slots, which can receive additional DIMMs as the computer memory needs of the user increase. However, the electrical terminals within the empty electrical slots are disadvantageously susceptible to corrosion, which may affect the performance of the DlMMs once they are inserted into the empty slots. Therefore, a need exists for a way to provide capacity to expand memory while avoiding the susceptibility to corrosion or other damage.
The various electrical components located on the backplane and cards (for example, the DIMMs on the memory riser card) tend to consume a substantial amount of electrical power, and therefore generate a substantial amount of heat. Because excess temperature can impair computer system reliability and functionality, computer systems are typically provided with one or more large, high-powered blowers that cause a cooling flow of air to pass through the cage, and over the various electrical components, thus causing a transfer of heat away from the electrical components.
However, the various electrical components generate different amounts of heat, depending on the amount of electrical power the respective electrical component consumes. In order to sufficiently cool the electrical components which generate the most heat, the size of the blower is typically dependent on the amount of air flow necessary to cool these highest powered electrical components. For example, if there is one electrical component on a processor card, for example, which requires 25 cubic feet per minute of cooling air to dissipate its generated heat, but the remaining electrical components only require 15 cubic feet per minute of cooling air to dissipate their generated heat, the blower must blow at least 25 cubic feet per minute over all the electrical components, so as to cool the electrical component on the processor card, i.e., the electrical component which generates the most heat. Thus, more cooling air than necessary is supplied to the other, lower powered electrical components. Therefore, a need exists for a cooling system which can provide the optimum required cooling air to each of the components without wasted capacity.
Because of their large outputs, the known blowers disadvantageously generate a substantial amount of noise, which requires bulky and expensive acoustic dampening material to be provided within the computer's housing. Moreover, these high-output blowers are typically relatively large, and disadvantageously take up a large amount of space within the computer housing. Further, high-output blowers are relatively expensive, as compared to low-output fans. Therefore, a need exists for a cooling system without these disadvantages.
A typical goal in the computer industry is to create a computer system which has increased computing power in a smaller computer housing. For example, present low end deskside or computer workstations have capabilities which meet or exceed those capabilities of high end systems developed for business use only a few years ago. However, as computer power increases, cooling demands increase, as described above. As computer size is decreased, it becomes necessary to make more efficient use of less and less space. Since the cooling capacity of a system is related to the volume of air which can be transported therethrough, the goal of increased computing power in decreased housing size presents challenges to system designs. Further, today's low end computer market is highly cost competitive. Therefore, a need exists for an inexpensive, high performance, compact deskside computer system.